I think there is sometimes a conflict over gift expectations, as camlan says, and it can be hard to see when you (general) have tipped over the line--you're so excited about getting specific things, or being able to take a trip you couldn't afford on your own, or something like that, and then someone goes and gives you something that does not fit with this plan. We're only human, it can be hard to take a step back and realize, "No, I should be grateful for this gift, no matter what it is." (I do think there are mean-spirited, dismissive gifts that one does not need to be grateful for, but I don't think that's the case here.)
For example, my friend Amy put things on her wedding registry and baby shower registry, and she wanted those things, not something similar, not a cheaper version, not a different color. She's pragmatic and decisive, she researched everything before deciding on it, and she truly didn't understand why someone would get her something different. She wanted sage green towels in brand X, someone gave her chocolate brown towels in brand Y. Why? Obviously they didn't realize that the color, brand, and store were selected very carefully, and that she will immediately take the brown towels back to the store without even unfolding them. I think I accompanied her on at least 3 trips to return things to stores, before the wedding even took place. And returning something to a store is not always the fastest or most pleasant experience, and you start thinking more about the time and inconvenience and gas, and "Why couldn't they have just given me something from my list?! Was that really so hard?!"
But of course, once you get too far down that path, I think you're in danger of becoming rude. I suppose if you always keep it to yourself, or at least don't let the giver know, you're functionally still good. But if it bleeds out into how you think about the person--"I really wanted X, why couldn't they just do that?"--that can be bad.
The bolded is something I cannot stand.
You throw the party / wedding that _you_ (general) can afford and you (general) take the honeymoon that _you_ (general) can afford.
I don't want to see a cash bar and a honeymoon registry because you (general) have decided that you (general) want to have a party or go on a holiday that you need me to subsidise.
I'm quite generous when it comes to wedding gifts. I don't mind parting with a bit of cash for a HC, but once they start telling me to give them this or that, it's the quickest way to make me tighten my purse strings.
I've never understood this line of reasoning. If a couple registers for china and linens and a bunch of appliances they couldn't otherwise afford on their own, that's okay? But if they prefer the experience of traveling together to a toaster, thats not ok?
No, that's not ok either, from my personal viewpoint.
I don't like gift registries of any kind. I cannot get on board with them. I think they are rude.
When I'm faced with one I tend to buy something from there but I do think the person a bit rude.
I know there are pro-registry people and anti-registry people out there and I can happily agree to disagree about the whole issue. I just happen to be one of the people in the anti-registry camp.
No hard feelings to anybody in the other camp
ETA: I removed a bit, because it's not probably true of my feelings. Also to add that my standard wedding gift these days (for those who do not have registries) is cash and so far I've had no complaints .
Cash is always fine, of course, and can be the best bet if the giver is unsure of the HC's preferences.
However, I politely differ with a PP's assertion that anyone close enough to the HC to be invited to the wedding will already know their preferences. Maybe, maybe not. They might have been living in bare-bones student housing previously, and will be relocating to a new, much larger place after the wedding. Or, the bride might have a dear great-aunt who has corresponded with her regularly, but has not visited her since she moved out of her parents' home eight years earlier. In either case, the guest likely won't have any idea of the new preferences.
Again, guests are free to not use the registry but one of its purposes is to help avoid duplications or "too many". For example, I know brides today seldom register for china, but years ago it was pretty common. And a mainstream, fairly affordable line like Royal Albert used to cost about $50 a place-setting on sale so it was quite a common gift for guests who like to give china. But say the HC registered for eight settings (they wouldn't be able to seat any more at their table) - this would help prevent them receiving ten settings, and either returning the extra two, or storing them somewhere indefinitely. Even today, maybe they enjoy coffee/lattes and someone learns that they'd like a Tassimo. If they haven't registered, they could end up with a half-dozen of them.